Deodorizing and sterilizing device having catalyst deterioration sensing function

ABSTRACT

A deodorizing and disinfecting apparatus having catalyst deterioration detection function of the present invention comprises: an air supply portion for inhaling air inside; an ozone generating portion for discharging ozone to the inhaled air: a catalyst for accelerating deodorizing and disinfecting actions and decomposition of the ozone disposed downstream from the ozone generating portion; an ozone sensor for detecting the concentration of remaining ozone disposed downstream from the catalyst; and means for repeating a cycle including stop of ozone discharge from the ozone generating portion for a predetermined time period when the concentration of the remaining ozone reaches a predetermined concentration or more, and for determining that the catalyst is deteriorated when a condition wherein an interval between times when the concentration of the remaining ozone is not less than a predetermined concentration becomes shorter than a predetermined time period is recognized at a predetermined frequency, and then for stopping discharge of the ozone.

TECHNICAL FIELD

The present invention relates to a deodorizing and disinfectingapparatus using ozone.

BACKGROUND ART

Since ozone exhibits a strong oxidizing action, it has been used in manyfields such as water treatment, medical and food industries in recentyears, in order to perform deodorization, disinfection and the like.Lately, attention has been paid to ozone for use in variouscountermeasures for odors in living spaces, and many apparatuses usingozone have been developed.

As described above, ozone exhibits such useful action. However, ozoneitself has special odor. Therefore, when ozone is used for an apparatus,it is necessary to prevent ozone from being discharged to the outside ofthe apparatus. For this reason, ozone remaining after treatment issubjected to a thermal decomposition method or a decomposition methodwith a catalyst. Among these methods, the method with the catalyst isrelatively simple, and thus generally used. However, in the method ofdecomposing ozone by using the catalyst, there is apprehension that theactivity of the catalyst lowers gradually, and ozone in an excessiveconcentration is discharged to the outside of the apparatus after usefor a long period of time or because of changes in environmentalconditions or the like.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a highly reliabledeodorizing and disinfecting apparatus capable of preventing a dischargeof remaining ozone to the outside of the apparatus even when thecatalyst is deteriorated.

The present invention provides an ozone deodorizing and disinfectingapparatus comprising an ozone generating portion, a catalyst havingfunctions for accelerating ozone deodorizing and disinfecting actionsand for decomposing the ozone, an ozone sensor and an air supplyportion, and additionally having functions for repeating a cycleincluding temporary stop of ozone discharge when the concentration ofozone remaining after treatment by the catalyst reaches a predeterminedconcentration or more and resumption of ozone discharge after an elapseof a predetermined time period, and then for determining that thecatalyst has been deteriorated when a tendency wherein an intervalbetween times when the concentration of the remaining ozone reaches apredetermined concentration becomes shorter than a predetermined timeperiod is recognized at a predetermined frequency.

The deodorizing and disinfecting apparatus having the catalystdeterioration detection function of the present invention comprises: anair supply portion for inhaling air inside; an ozone generating portionfor discharging ozone to the inhaled air; a catalyst for acceleratingthe deodorizing and disinfecting actions and for decomposition of ozone,disposed downstream from the ozone generating portion; and an ozonesensor for detecting the concentration of remaining ozone, disposeddownstream from the catalyst; and further comprising means for repeatinga cycle including stop of ozone discharge from the ozone generatingportion for a predetermined time period when the ozone sensor detectsthat the concentration of the remaining ozone is not less than apredetermined concentration, and for determining that the catalyst hasbeen deteriorated when a condition wherein an interval between timeswhen the concentration of the remaining ozone in the continuous cyclesis not less than a predetermined concentration becomes shorter than apredetermined time period is recognized at a predetermined frequencythereby stopping ozone discharge.

Furthermore, it is preferable that the apparatus further comprises alarmmeans for notifying that the catalyst has been deteriorated when thecatalyst is determined to be deteriorated and ozone discharge isstopped. By this means, the user can be accurately notified of the needfor replacement of the catalyst by indication, alarm sound or the like.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional schematic view showing a deodorizing anddisinfecting apparatus in accordance with an embodiment of the presentinvention.

FIG. 2 is a block diagram showing a catalyst deterioration determinationsystem of the same apparatus.

FIG. 3 is a flowchart showing a configuration of the signal processingportion of the apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be detailed below referring tothe drawings.

The basic structure of the deodorizing and disinfecting apparatus havingthe catalyst deterioration detection function in accordance with thepresent embodiment is shown in FIG. 1.

Air outside the apparatus is inhaled into the apparatus from an airsuction port 6 by a fan 3. At this time, by a filter 7 disposed at theair suction port 6, dirt, dust and the like included in the influent airare removed. Next, a predetermined amount of ozone generated by an ozonegenerator 1 is delivered to the air. The air and the ozone are mixednearly uniformly by a diffusion plate 8. Then, by mixing with the ozone,contaminants such as odor components and bacteria in the air aredecomposed and removed. In addition, the air mixed with the ozone makescontact with a catalyst 2, whereby the actions of the ozone fordecomposing and removing the contaminants are accelerated, anddecomposition of the remaining ozone is also accelerated.

After the air inhaled into the apparatus is thus subjected todeodorizing and disinfecting treatment and cleaned, it is dischargedfrom a clean air discharge port 9 to the outside of the apparatus.

Upstream from the clean air discharge port 9, an ozone sensor 4 isdisposed to detect the concentration of the remaining ozone in the cleanair. The ozone sensor 4 delivers a signal corresponding to the detectedconcentration of the remaining ozone to a signal processing portion 5.

The signal processing portion 5 is provided with a memory portion 51, acalculating portion 52 and a control portion 53 as shown in FIG. 2.

In the memory portion 51, the allowable upper limit concentration of theremaining ozone, a time period required when the air downstream from thecatalyst 2 in a condition including no ozone reaches the allowable upperlimit ozone concentration while the catalyst 2 functions properly(hereinafter, referred to as a standard detection interval), and astandard detection time period for determining that the catalyst isdeteriorated have been stored.

The calculating portion 52 compares the concentration of the remainingozone on the basis of the output signal of the ozone sensor 4 with theallowable upper limit concentration thereby to determine whether theconcentration is less than the allowable upper limit concentration ornot. At this time, if the calculating portion 52 determines that theconcentration of the remaining ozone is not less than the allowableupper limit concentration, it delivers a signal for temporarily stoppingozone discharge by the ozone generator 1 for a predetermined time periodto the control portion 53. Therefore, the concentration of the remainingozone decreases temporarily. However, when ozone discharge by the ozonegenerator 1 is resumed, the concentration of the remaining ozoneincreases and exceeds the allowable upper limit concentration again. Thecalculating portion 52 thus measures a time period after determiningthat the concentration of the remaining ozone was not less than theallowable upper limit concentration until the concentration of theremaining ozone is determined to be not less than the allowable upperlimit concentration again (hereinafter referred to as a detectioninterval). When the detection interval becomes not more than thestandard detection interval, the calculating portion 52 counts thenumber of the times, and compares it with the preset standard detectiontimes. When the number of the times reaches the standard detectiontimes, the calculating portion 52 determines that the catalyst 2 hasbeen deteriorated and delivers a signal for stopping ozone discharge bythe ozone generator 1 to the control portion 53.

In accordance with the signal from the calculating portion 52, thecontrol portion 53 controls the ozone generator 1, and also controls asignal for indication, alarm or the like.

If the detection interval is longer than the standard detectioninterval, the activity of the catalyst 2 is determined to be normal, andthe same cycle is repeated. The air deodorizing and disinfectingtreatment thus continues. However, if the detection interval is shorterthan the standard detection interval, and if a similar tendency isrecognized a predetermined number of times, the catalyst 2 is determinedto be deteriorated, and ozone discharge by the ozone generator 1 isstopped. The standard detection interval is set in consideration of theamount of ozone discharged by the ozone generator 1, a time period fortemporarily stopping discharge, and the like. In addition, although itis not shown, deterioration of the catalyst is notified by an indicationor an alarm sound.

Embodiment 1

In the present embodiment, the examinations described below wereconducted by using a deodorizing and disinfecting apparatus having acatalyst deterioration detection function, which is similar to theabove-mentioned apparatus.

The ozone generator 1 is provided with creepage discharge type ozonegenerating electrodes comprising an induction electrode and a dischargeelectrode formed on an alumina substrate, which generates ozone byso-called silent discharge. A thin-film sensing element mainlycomprising a composite oxide containing In₂ O₃ and SnO₂ at a molar ratioof Sn/(In+Sn)=3/100 was used as the ozone sensor 4. The catalyst 2 has ashape of honeycomb having a volume of about 100 cm³, and is made of ametal oxide mainly comprising Mn.

As setting conditions, the allowable upper limit concentration of theremaining ozone was set at 0.05 ppm, the standard detection intervalbetween two continuous times was set at 3 minutes, and a temporary ozonestopping time period was set at 30 seconds. Furthermore, when thedetection interval became shorter than the above-mentioned standarddetection interval five times continuously, the catalyst 2 wasdetermined to be deteriorated.

Referring to the flowchart shown in FIG. 3, the catalyst deteriorationdetection function of the deodorizing and disinfecting apparatus inaccordance with the present embodiment is described below.

When the apparatus is operated, the fan 3 starts suction, and the ozonegenerator 1 starts ozone discharge. The ozone sensor 4 detects ozonecontinuously during the operation of the apparatus. At step 101, if theactivity of the catalyst 2 is lowered, and the concentration of theremaining ozone is determined to be reached the allowable upper limitconcentration (0.05 ppm), the signal processing portion 5 measures timeT_(o) used as a start point. At the same time, the signal processingportion 5 delivers a signal for temporarily stopping ozone discharge tothe ozone generator 1. By this signal, the concentration of theremaining ozone is lowered temporarily. After a lapse of predeterminedtime period t_(p) (30 seconds) from the stop of ozone discharge, ozonedischarge is resumed.

Next, at step 102, when the concentration of the remaining ozone becomesnot less than the allowable upper limit concentration again, time T₁ ismeasured, and a detection interval (T₁ -T_(o)) is calculated. Inaddition, at the same time, ozone discharge is stopped. Then, the samecycle of resuming ozone discharge and calculating the detection interval(T_(n) -T_(n-1) : n is the number of cycles) when the concentration ofthe remaining ozone reaches the allowable upper limit concentration inthe same way is repeated. At step 103, the number of times wherein thedetection intervals are determined continuously to have been shorterthan the standard detection interval (3 minutes) is counted.

If the detection interval is determined to have been not less than thestandard detection interval before the count number reaches five, thecount number is canceled once, ozone discharge is resumed after a lapseof t_(p), and the same cycle for calculating the detection interval isrepeated.

At step 104, when the count number reaches five, that is, when thedetection interval becomes shorter than the standard detection intervalfive times continuously, the signal processing portion 5 delivers asignal for stopping ozone discharge to the ozone generator 1, and theapparatus stops.

The operation of the apparatus with conditions being set as describedabove was confirmed.

After a space having a volume sufficiently larger than the volume of theapparatus (about 1000 times as large as the volume of the apparatus) wasfilled with clean air, and the apparatus having been set in theabove-mentioned conditions was installed in the space, and the space washermetically sealed. Next, the fan 3 was operated, and the air outsidethe apparatus was inhaled at a flow rate of 7 liters/minute. Inaddition, ozone was generated and discharged by the ozone generator 1 sothat the ozone concentration in the air was about 0.06 ppm, exceedingthe decomposition capability of the catalyst 2. However, the ozone to bedischarged from the clean air discharge port 9 to the outside of theapparatus was discharged to the outside the hermetically sealed space soas not to be inhaled again into the apparatus.

The detection interval, which was about 7 minutes immediately after thestart, became shorter gradually, and became 2.5 minutes at the 30thcycle, shorter than the standard detection interval of 3 minutes. Afterthis, the detection interval became about 2 minutes, and a cycle havinga detection interval shorter than the standard detection interval wasrepeated five times. At this time, ozone discharge was stopped.

In this way, it is confirmed that the present apparatus operatesproperly.

Embodiment 2

In the present embodiment, a case of newly added conditions to improvethe accuracy of catalyst deterioration detection in addition to the sameconditions as those for embodiment 1 is described.

In the present embodiment, by using the same apparatus as that forembodiment 1, in addition to the same determination conditions as thosefor embodiment 1, it was also determined that deterioration has occurredin the case when a cycle having a detection interval shorter than thestandard detection interval of 3 minutes was recognized 4 times or morewhile detection cycles were repeated 6 times. According to this method,improper determination can be prevented even in the case that thecatalyst should be determined to be deteriorated essentially but thedetection interval becomes longer than the standard detection intervalbecause of some factors such as decrease in the amount of ozone, changein fan capability and the like.

In the present embodiment, first, the concentration of ozone dischargedby the ozone generator was set at 0.06 ppm. In addition to this, when acycle wherein the detection interval became shorter than the standarddetection interval continued 3 times, the concentration of thedischarged ozone was set at 0.03 ppm by adjusting the ozone generator.At this time, the detection interval became about 3.5 minutes. After anelapse of about 5 minutes, when the concentration of the dischargedozone was returned to its initial condition, the next detection intervalbecame less than 3 minutes. In this way, at a stage wherein detectionintervals less than 3 minutes were recognized in six detection cycles intotal, the catalyst was determined to be deteriorated, and ozonedischarge was stopped.

The present apparatus was operated continuously in actual livingenvironments and its function was confirmed.

The present apparatus was installed in a living room having a volume ofabout 50 m³, and operated continuously; as a result, after an elapse ofabout 2500 hours, the catalyst was determined to be deteriorated, andozone discharge was stopped. At this time, the catalyst was taken out ofthe apparatus. When the ozone decomposition activity of the catalyst wasmeasured, it was found that the activity was lowered to about 55% of itsinitial activity.

The ozone generator, the ozone sensor, the catalyst and the like usedfor the present invention can be replaced with others if they have thesame functions as those used for the embodiments, provided that they donot disagree with the purpose of the present invention. For example,metal oxides such as In₂ O₃, SnO₂, Co₃ O₄, NiO, CuO and V₂ O₅, orcomposite oxides of these can be used for the ozone sensor. In addition,the structure of the apparatus can also be adapted in accordance withconditions corresponding to its capability and operation environment.The deterioration determination conditions are not limited to those ofthe embodiments, but the count number of detection intervals, which areshorter than the standard detection interval, can be increased forexample.

Industrial Usability

Since deterioration of a catalyst for a deodorizing and disinfectingapparatus using ozone can be detected and determined with reliability inthe present invention, it is possible to prevent discharge of excessiveamounts of ozone to the outside the apparatus. Therefore, thedeodorizing and disinfecting apparatus having the catalyst deteriorationdetection function of the present invention is expected to be usedwidely in many fields such as water treatment, medical and foodindustries.

We claim:
 1. A deodorizing and disinfecting apparatus having a catalystdeterioration detection function comprising: an air supply portion forinhaling air; an ozone generating portion for discharging ozone to theinhaled air; a catalyst for accelerating the deodorizing anddisinfecting actions and decomposition of said ozone, disposeddownstream from said ozone generating portion; an ozone sensor fordetecting the concentration of remaining ozone, disposed downstream fromsaid catalyst; and means for repeating a cycle including stop of ozonedischarge from said ozone generating portion for a predetermined timeperiod when the concentration of said remaining ozone reaches apredetermined concentration or more, and for determining that saidcatalyst has been deteriorated when a condition wherein an intervalbetween times when the concentration of said remaining ozone is not lessthan the predetermined concentration becomes shorter than apredetermined time interval is recognized at a predetermined frequency,and then for stopping discharge of said ozone.
 2. The deodorizing anddisinfecting apparatus having a catalyst deterioration detectionfunction in accordance with claim 1, wherein said apparatus furthercomprising alarm means for notifying that said catalyst has beendeteriorated when said catalyst is determined to be deteriorated and theozone discharge is stopped.
 3. A method of preventing discharge ofexcessive amounts of ozone from a deodorizing and disinfecting apparatususing ozone, comprising an ozone sensor, a signal processing unit, andan ozone generator, the method comprising the steps of:a) stopping ozonegeneration in said ozone generator when the ozone sensor senses that theamount of ozone discharged from said deodorizing and disinfectingapparatus has reached an allowable limit; b) resuming generation ofozone in said ozone generator after an elapsed time period; c) stoppingozone generation in said ozone generator when the ozone sensor sensesthat the amount of ozone discharged from said deodorizing anddisinfecting apparatus has reached the allowable limit again; d)counting the number of times a detection interval is less than astandard detection interval, said detection interval being the amount oftime between successive sensing operations in which the amount of ozonehas reached the allowable limit; e) stopping the operation of saiddeodorizing and disinfecting apparatus when said signal processing unitdetermines that the number of times that said detection interval isdetected to be less than a standard detection interval is greater than apredetermined number.
 4. The method of preventing discharge of excessiveamounts of ozone from a deodorizing and disinfecting apparatus in claim3,wherein step e) further comprises the step of generating an alarm whensaid signal processing unit determines that the number of times thatsaid detection interval is detected to be less than a standard detectioninterval is greater than said predetermined number.
 5. The method ofpreventing discharge of excessive amounts of ozone from a deodorizingand disinfecting apparatus in claim 3,wherein step e) further comprisesthe steps of: counting the number of times said detection interval isdetected to be less than a standard detection interval; and determiningwhether the counted number has reached said predetermined number.
 6. Themethod of preventing discharge of excessive amounts of ozone from adeodorizing and disinfecting apparatus in claim 5,wherein saidpredetermined number is five.
 7. The method of preventing discharge ofexcessive amounts of ozone from a deodorizing and disinfecting apparatusin claim 3, the deodorizing and disinfecting apparatus furthercomprising a catalyst for accelerating the deodorizing and disinfectingactions and the decomposition of said ozone, the method furthercomprising the step of:determining the catalyst to be deteriorated whensaid signal processing unit determines that the number of times thatsaid detection interval is detected to be less than a standard detectioninterval is greater than said predetermined number.